1. Field of the Invention
The invention generally relates to aircraft area navigation systems, particularly with regard to effecting lateral transitions with regard to the waypoints of the flight plan.
2. Description of the Prior Art
Aircraft area navigation systems, hereinafter referred to as RNAV, are known in the prior art that transition the aircraft from the inbound course or leg of a waypoint to the next leg thereof by merely switching from the first track to the next at a predetermined distance from the waypoint and permitting the steering signals to capture the next leg by either manual pilot control through the flight director or by applying the steering signals to the automatic flight control system. This prior art procedure, particularly in the automatic mode, provides an exponential capture of the next track utilizing a blend of cross track deviation and track angle error. Since the prior art approach assumes the absence of non-linearities such as roll attitude limits (unrestricted bank angle commands) and, in practice, the bank angle commands are necessarily limited for safety and passenger comfort, undesirable overshooting or hunting (S turning) of the next leg results thereby utilizing an excessive amount of air space in a relatively uncontrolled manner. Additionally, at the point of leg switching large deviation signals are generated which result in presenting an undesirable large deviation indication and a sudden shift in the commanded heading to the human pilot via the flight instruments. When the displayed deviation is at or near its maximum value, the pilot is unable to maintain cognizance of the aircraft position. Although this prior art track transitioning technique has satisfied aviation regulatory agency present day requirements with regard to aircraft spacing when transitioning from one course to another, potential precise future requirements of "guidance around corners" with regard to aircraft spacing will not be so satisfied.